NOTES. IX 



in comparison with the density of their aggregates (the entire body), lead, in 

 following atomic hypotheses, to the result, that the distance of the mole- 

 cules from each other is much greater than their diameters. 



( 41 ) p. 24. Kosmos, Bd. i. S. 98102 (English edit. Vol.i. p. 8589). 



(45) p> 24 Id. Bd. i. S. 39 and 50 5G (English, edit. Vol. i. p. 40 and 

 4250). 



(46) p 24 Wilhelm von Humboldt, Gesamrnelte Werke, Bd. i. S. 23. 



( 47 ) p. 26. Kosmos, Bd. i. S. 80 and 81 (English edition, Vol. i. 

 p, 68 and 69). 



(43) p 27. Id. S. 51 (English edition, p. 44). 



(49) p . 27. Halley, in the Phil. Trans, for 1717, Vol. xxx. p. 736. 



( 50 ) p. 28. Pseudo-Plut. de plac. Philos. ii. 1516; Stob. Eclog. phys. 

 p. 582 ; Plato, in Tim. p. 40. 



( 51 ) p. 28. Macrob. Somn. Scip. i. 9 10 ; " stellee inerrantes," in Cicero 

 de Nat. Deorum, iii. 20. 



( 52 ) p. 28. The principal passage in which the technical expression, 

 evSeSe^eW ito-rpa, occurs, is Aristot. de Ccelo, ii. 8, p. 289, lin. 34 ; p. 290, 

 lin. 19, Bekker. This alteration of the nomenclature had previously arrested 

 my attention when engaged in examinations respecting Ptolemy's optics, and 

 his experiments on the refraction of rays. Professor Franz, of whose philo- 

 logical learning I have often been glad to avail myself, remarks that 

 Ptolemy (Syntax, vii. 1) also says of the fixed stars #arep 7rpo(nre<j>u/c($Tes- 

 as if fastened to the sky. Ptolemy blames the expression ff&aipa dirAavvis 

 (orbis inerrans), remarking that, "inasmuch as the stars always preserve 

 their distances from each other, we may justly term them dirhave'is ; but 

 inasmuch as the whole sphere to which they are attached is in motion, the 

 name air^av^s seems but little suited thereto." 



( 53 ) p. 28. Cicero de Nat. Deor. i. 13; Plin. ii. 6 and 24; Manilius, 

 ii. 33. 



( 54 ) p. 30. Kosmos, Bd. i. S. 91 (English edition, Vol. i. p. 78). 

 Compare Encke's excellent considerations on the Arrangement of the 

 Sidereal System, 1844, S. 7. 



( M ) p. 31. Kosmos, Bd. i. S. 162 (English edition, Vol. i. p. 145). 

 ( 5G ) p. 31. Aristot. de Ccelo, i. 7, p. 276, Bekker. 

 ( 57 ) p. 31. Sir John Hersehel, Outlines of Astronomy, 1849, 803, 

 p. 541. 



